Typical tunable micro-lenses existing in reports can be categorized as three types. The first category is the electrowetting tunable lenses. After a large electric field is applied at the interface of a liquid lens and a solid structure, the contact angle as well as the surface profile of the liquid lens are changed. The interface friction and the evaporation of liquid problems cannot be ignored. The second category is the liquid-filled lens approach. The main idea is to deform a liquid-filled chamber, which acts as a lens, via an external pressure source. This approach provides a large tuning range. However, an additional pressure source is required, and the self-weight of the liquid may introduce an undesired deformation. The third category is the liquid crystal immersed approach. This method directly changes a refraction index of a liquid crystal to modify the focal length. However it is difficult to realize a Micro-Opto-Electro-Mechanical System (MOEMS) due to the severe optical aberration induced by fringe effects.
The complicated fabrication process and complex control requirements of the above tunable micro-lenses significantly limit the potential applications. Furthermore, it is difficult to miniaturize the above tunable micro-lenses to a millimeter scale or a even smaller scale. The requirements of easy fabrication and integration are hard to be satisfied simultaneously by the existing approaches.
Hence, because of the defects in the prior arts, the inventors provide a solid tunable micro optical device to effectively overcome the demerits existing in the prior arts. In comparison with other tunable micro-lens systems, the present invention has the following characteristics. Firstly, the tunable lens of the present invention is composed of only solid-state polymer material, and no phase transition is required during operation. Secondly, the fabrication process for the present invention is easy and has a very high yield rate. Thirdly, the device of the present invention requires no extra pumping system, which is required in a liquid filled lens system, so that the tunable micro-lens of the present invention can be stand-alone. These characteristics make the device of the present invention suitable to be integrated with micro-optical systems.